1. Field of the Invention
The present invention relates to a cathode plate for use in a non-aqueous electrolyte secondary battery such as lithium-ion secondary battery, to a non-aqueous electrolyte secondary battery using the same, and to a method for producing the cathode plate for a non-aqueous electrolyte secondary battery.
2. Background Art
Non-aqueous electrolyte secondary batteries represented by lithium-ion secondary batteries have high energy density and high voltage, and do not cause the memory effect (a phenomenon in which a battery gradually loses its capacity when the battery is charged before the battery is completely discharged) on charge or discharge. The non-aqueous electrolyte secondary batteries are therefore used in various fields of portable devices, large-sized devices, and so forth. Further, in recent years, the use of secondary batteries in the fields of electric vehicles, hybrid vehicles, power tools, etc. that are needed to have high output characteristics has attracted public attention.
A non-aqueous electrolyte secondary battery is generally composed of an anode plate, a cathode plate, a separator, and an organic electrolyte. For the anode plate and the cathode plate is usually used an electrode active material layer formed in the following manner: an electrode active material layer-forming coating liquid in the form of a slurry is applied to the surface of a current collector made of metal foil or the like, and is then dried with hot air or the like, and the dried film is pressed with a roller press or the like.
The electrode active material layer-forming coating liquid is a slurry prepared by kneading and/or dispersing in an organic solvent an electrode active material, a resinous binder, and a conductive material (provided that when the active material also has electrical conductivity, the conductive material may not be used), and other materials as needed. It is a conventional manner in which an electrode having an electrode active material layer is produced is that the above electrode active material layer-forming coating liquid is applied to the surface of a current collector and then dried, and the coating film formed on the current collector in this manner is pressed (e.g., paragraphs [0019] to [0026] of the specification of Patent Document 1; and paragraphs [0051] to [0055] of the specification of Patent Document 2 and [Claim 1] attached to the specification).
The electrode active material to be incorporated in the electrode active material layer-forming coating liquid is a particulate compound dispersible in the coating liquid and hardly fixes to the surface of a current collector when the coating liquid is simply applied to the current collector surface. Besides, a coating film formed by applying an electrode active material layer-forming coating liquid containing no resinous binder to a current collector and drying the applied coating liquid easily peels off the current collector. That is to say, electrode active material particles are bound together and are also fixed to the surface of a current collector through a resinous binder, whereby an electrode active material layer is formed. Thus, a resinous binder has been considered to be a substantially essential ingredient in the prior art.
On the other hand, the above conductive material is used to ensure good electronic conduction between the electrode active material in the electrode active material layer and the current collector, thereby decreasing the volume resistivity of the electrode active material layer itself.